// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_PROCESS_MANAGER_H_
#define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_PROCESS_MANAGER_H_

#include <map>
#include <memory>
#include <vector>

#include "base/callback.h"
#include "base/gtest_prod_util.h"
#include "base/memory/weak_ptr.h"
#include "base/synchronization/lock.h"
#include "content/common/service_worker/service_worker_status_code.h"

class GURL;

namespace content {

class BrowserContext;
struct EmbeddedWorkerSettings;
class SiteInstance;

// Interacts with the UI thread to keep RenderProcessHosts alive while the
// ServiceWorker system is using them. It also tracks candidate processes
// for each pattern. Each instance of ServiceWorkerProcessManager is destroyed
// on the UI thread shortly after its ServiceWorkerContextWrapper is destroyed.
class CONTENT_EXPORT ServiceWorkerProcessManager {
public:
    // |*this| must be owned by a ServiceWorkerContextWrapper in a
    // StoragePartition within |browser_context|.
    explicit ServiceWorkerProcessManager(BrowserContext* browser_context);

    // Shutdown must be called before the ProcessManager is destroyed.
    ~ServiceWorkerProcessManager();

    // Synchronously prevents new processes from being allocated
    // and drops references to RenderProcessHosts. Called on the UI thread.
    void Shutdown();

    // Returns true if Shutdown() has been called. May be called by any thread.
    bool IsShutdown();

    // Returns a reference to a running process suitable for starting the Service
    // Worker at |script_url|. Posts |callback| to the IO thread to indicate
    // whether creation succeeded and the process ID that has a new reference.
    //
    // Allocation can fail with SERVICE_WORKER_PROCESS_NOT_FOUND if
    // RenderProcessHost::Init fails.
    void AllocateWorkerProcess(
        int embedded_worker_id,
        const GURL& pattern,
        const GURL& script_url,
        bool can_use_existing_process,
        const base::Callback<void(ServiceWorkerStatusCode,
            int process_id,
            bool is_new_process,
            const EmbeddedWorkerSettings&)>& callback);

    // Drops a reference to a process that was running a Service Worker, and its
    // SiteInstance.  This must match a call to AllocateWorkerProcess.
    void ReleaseWorkerProcess(int embedded_worker_id);

    // Sets a single process ID that will be used for all embedded workers.  This
    // bypasses the work of creating a process and managing its worker refcount so
    // that unittests can run without a BrowserContext.  The test is in charge of
    // making sure this is only called on the same thread as runs the UI message
    // loop.
    void SetProcessIdForTest(int process_id)
    {
        process_id_for_test_ = process_id;
    }

    // Sets the process ID to be used for tests that force creating a new process.
    void SetNewProcessIdForTest(int process_id)
    {
        new_process_id_for_test_ = process_id;
    }

    // Adds/removes process reference for the |pattern|, the process with highest
    // references count will be chosen to start a worker.
    void AddProcessReferenceToPattern(const GURL& pattern, int process_id);
    void RemoveProcessReferenceFromPattern(const GURL& pattern, int process_id);

    // Returns true if the |pattern| has at least one process to run.
    bool PatternHasProcessToRun(const GURL& pattern) const;

private:
    FRIEND_TEST_ALL_PREFIXES(ServiceWorkerProcessManagerTest, SortProcess);
    FRIEND_TEST_ALL_PREFIXES(ServiceWorkerProcessManagerTest,
        FindAvailableProcess);
    FRIEND_TEST_ALL_PREFIXES(ServiceWorkerProcessManagerTest,
        AllocateWorkerProcess_FindAvailableProcess);
    FRIEND_TEST_ALL_PREFIXES(ServiceWorkerProcessManagerTest,
        AllocateWorkerProcess_InShutdown);

    // Information about the process for an EmbeddedWorkerInstance.
    struct ProcessInfo {
        explicit ProcessInfo(const scoped_refptr<SiteInstance>& site_instance);
        explicit ProcessInfo(int process_id);
        ProcessInfo(const ProcessInfo& other);
        ~ProcessInfo();

        // Stores the SiteInstance the Worker lives inside. This needs to outlive
        // the instance's use of its RPH to uphold assumptions in the
        // ContentBrowserClient interface.
        scoped_refptr<SiteInstance> site_instance;

        // In case the process was allocated without using a SiteInstance, we need
        // to store a process ID to decrement a worker reference on shutdown.
        // TODO(jyasskin): Implement http://crbug.com/372045 or thread a frame_id in
        // so all processes can be allocated with a SiteInstance.
        int process_id;
    };

    // Maps the process ID to its reference count.
    typedef std::map<int, int> ProcessRefMap;

    // Maps registration scope pattern to ProcessRefMap.
    typedef std::map<const GURL, ProcessRefMap> PatternProcessRefMap;

    // Returns a process vector sorted by the reference count for the |pattern|.
    std::vector<int> SortProcessesForPattern(const GURL& pattern) const;

    // Returns the id of an available process for this pattern, or
    // ChildProcessHost::kInvalidUniqueID if there is none.
    int FindAvailableProcess(const GURL& pattern);

    // Guarded by |browser_context_lock_|.
    // Written only on the UI thread, so the UI thread doesn't need to acquire the
    // lock when reading. Can be read from other threads with the lock.
    BrowserContext* browser_context_;

    // Protects |browser_context_|.
    base::Lock browser_context_lock_;

    // All fields below are only accessed on the UI thread.

    // Maps the ID of a running EmbeddedWorkerInstance to information about the
    // process it's running inside. Since the Instances themselves live on the IO
    // thread, this can be slightly out of date:
    //  * instance_info_ is populated while an Instance is STARTING and before
    //    it's RUNNING.
    //  * instance_info_ is depopulated in a message sent as the Instance becomes
    //    STOPPED.
    std::map<int, ProcessInfo> instance_info_;

    // In unit tests, this will be returned as the process for all
    // EmbeddedWorkerInstances.
    int process_id_for_test_;
    int new_process_id_for_test_;

    // Candidate processes info for each pattern, should be accessed on the
    // UI thread.
    PatternProcessRefMap pattern_processes_;

    // Used to double-check that we don't access *this after it's destroyed.
    base::WeakPtr<ServiceWorkerProcessManager> weak_this_;
    base::WeakPtrFactory<ServiceWorkerProcessManager> weak_this_factory_;
};

} // namespace content

namespace std {
// Specialized to post the deletion to the UI thread.
template <>
struct CONTENT_EXPORT default_delete<content::ServiceWorkerProcessManager> {
    void operator()(content::ServiceWorkerProcessManager* ptr) const;
};
} // namespace std

#endif // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_PROCESS_MANAGER_H_
